As an alternative to vertebral fusion, various prosthetic discs have been developed. The first prosthetics embodied a wide variety of ideas, such as ball bearings, springs, metal spikes and other perceived aids. These prosthetics are all made to replace the entire intervertebral disc space.
One approach to the intervertebral space is the transforaminal approach. This approach has been used in interbody lumbar fusion surgeries and involves approaching the intervertebral space through the intervertebral foramina. This approach often requires the removal of one facet joint on either the left or right side. After removal, the surgeon gains access to the intervertebral space through the intervertebral foramina. One drawback to this method is that the removal of a facet joint may lead to instability of the spine. Despite this drawback, in many instances the transforaminal approach is favored in that there is reduced risk to the organs and greater vessels (as compared to the anterior approach) and reduced risk to the spinal cord (as to the posterior approach).
Once a spinal disc is positioned, there may be a need to limit the motion of the disc and convert the disc implant into a fusion implant. This generally requires the removal of the disc and the insertion of additional implants. Therefore there is a need for a single implant that can be utilized to convert prosthetic disc into a fusion device tailored for use in a transforaminal approach.